1. Field of the Invention
The present invention relates to a binding assembly for retaining sheets of material, such as paper, and more particularly, to a binding assembly having a pair of side plates which are independently detachable from a base member so that sheets may be inserted or removed from either side of the binding assembly.
2. Description of the Background Art
Various binding assemblies are known in the prior art for retaining sheets of paper or other materials together in an orderly fashion. The binding assemblies are usually attached to a cover member to form a notebook or binder. Typically, a plurality of holes are punched along a side edge of sheets of paper, and pins or tubes of the binding assembly are passed through the holes to retain the sheets of paper together.
One example of such a binding device is shown in U.S. Pat. No. 4,693,625, which shows a binding assembly having a pair of side members which support a pair of pins and tubes onto which the sheets of paper are placed. The side members are detachable from a base member which is fixed to the spine of a notebook cover. Each of the side members includes a pair of engaging rods which are inserted into hollow portions in the base member to retain the side members to the base member. The engaging rods are movable along the length of the respective side member by a sliding plate disposed within the side member which is slidable along the length of the side member. The sliding plate transfers a force provided by a user in a direction of the length of the side member to the engaging rods, so that the side member may be detached from the base member. Unfortunately, the detaching mechanism is complicated, and therefore costly to produce. Further, because the side members must be relatively thick to accommodate the components of the detaching mechanism therein, there remains less room for the sheets of paper for a fixed width of binder cover, and thus the capacity of the binding assembly is limited. Finally, only short portions of the engaging rods are held by the hollow portions of the base member, and therefore the retaining strength is limited.
Another example of a binding device is shown in U.S. Pat. No. 5,330,280, which shows a binding assembly also having a pair of side members which support a pair of pins and tubes onto which the sheets of paper are placed. Each of the side members includes a pair of engaging rods which are inserted into hollow portions in the base member to detachably retain the side members to the base member. The engaging rods are movable along the length of the respective side member by an actuating mechanism which is slidable in the direction of the length of the side member. Similarly to the previously discussed patent, the actuating mechanism transfers a force provided by a user in the direction of the length of the side member to the engaging rods, so that the side member may be detached from the base member. A series of actuating mechanisms are shown in the various embodiments, all of which are extremely complex. However, as the number of components and the complexity of a device increases, the cost to manufacture increases, and the number of components that can malfunction increases. Further, since only short portions of the engaging rods are held by the hollow portions of the base member, the retaining strength is also limited.
A final example of a binding device is shown in U.S. Pat. No. 5,634,732, which shows a binding assembly also having a pair of side members which support a pair of pins and tubes onto which the sheets of paper are placed. Each of the side members includes a pair of fixed engaging rods which are retained by a pair of latches provided on the base member. The pair of latches are movable along the width of the base member by depressing an actuating knob attached to the latches. As the knob is pressed inwardly, the latches move inwardly, and allow the engaging rods to move therepast to release the side member. However, the placement and actuation direction of the latch assemblies promotes inadvertent release of the side members by contact of the actuating knob with the front or rear cover members of the notebook binder. Also, other materials located loosely within the notebook may become wedged between the cover member and the actuating knob, resulting in inadvertent release of the side members. Finally, the latch assemblies are made of plastic material, and are susceptible to increased wear and breakage.